The present invention relates to a cleaning apparatus for cleaning the surface of an image bearing member in a printer, a copying machine, a facsimile machine, and the like. It also relates to an image forming apparatus equipped with a cleaning apparatus.
In the field of a cleaning apparatus for an image forming apparatus such as a printer, a copying machine, a facsimile machine, and the like, a cleaning apparatus having a cleaning blade as a cleaning member for cleaning an image bearing member has been known.
In an electrophotographic image forming apparatus, for example, a toner image is formed on a photoconductive drum (image bearing member) through a plurality of image forming processes: a charging process, an exposing process, and a developing process. The toner image is transferred onto transfer medium (for example, paper) from the photoconductive drum through a transferring process. During this transferring process, all the toner, of which the toner image on the photoconductive drum is formed, is not transferred; a small amount of the toner remains on the peripheral surface of the photoconductive drum The toner remaining on the peripheral surface of the photoconductive drum (which hereinafter will be referred to as xe2x80x9cresidual tonerxe2x80x9d) is removed by the above described cleaning blade.
Referring to FIG. 9, the edge 61a of a cleaning blade 61 is placed in contact with the peripheral surface of a photoconductive drum 11, so that the residual toner adhering to the peripheral surface of the photoconductive drum 11 is scraped away by the cleaning blade 61.
However, a cleaning blade in accordance with the prior art, such as the above described one, suffers from the following problems.
Also referring to FIG. 9, as the residual toner is scraped away by the edge 61a of the cleaning blade 61 placed in contact with the peripheral surface of the photoconductive drum 11, it agglomerates in the adjacencies of the edge 61a. Normally, as the agglomeration of the residual toner grows to a certain size, it falls off into the cleaning apparatus shell (unshown) of the cleaning apparatus, creating no problem.
In recent years, however, it became evident that, due to the increase in the peripheral velocity (process speed) of the photoconductive drum 11 resulting from the increase in the speed of an image forming apparatus, the agglomeration of the toner kept on growing in size without falling, and that some of the toner particles slipped through the nip N between the edge 61a of the cleaning blade 61 and the photoconductive drum 11, and transferred onto a transfer medium (in the form of a sheet), forming stripes across the medium, during the following image formation cycle. This has been a serious problem. Incidentally, the severity of this problematic phenomenon also depends on the ambient conditions.
As for a method for improving the cleaning performance of a cleaning blade, a few have been disclosed. For example, Japanese Laid-open Patent Application Nos. 6-4014 and 11-174922 disclose a method which causes a cleaning blade to vibrate with the use of a piezoelectric element. This method, however, suffers from the following faults. That is, a piezoelectric element is attached to a cleaning blade, which deteriorates as its cumulative usage increases, and therefore, must be replaced. As the deteriorated cleaning blade is replaced with a fresh one, the piezoelectric element is replaced together with the deteriorated cleaning blade, resulting in cost increase, since the piezoelectric element is attached to the deteriorated cleaning blade. Further, it is difficult to vibrate sufficiently to remove the grown agglomeration of the residual toner. Japanese Laid-open Patent Application No. 9-160455 discloses a method which uses an impact to vibrate a cleaning blade. This method, however, suffers from the following problem: a certain behavior of a cleaning blade which occurs as the cleaning blade is vibrated by impact may allow the residual toner to slip through the nip N, although it may be possible to vibrate vigorously enough to remove the grown agglomeration of the residual toner.
According to Japanese Laid-open Patent Application No. 2000-112187, when a number of copies to be made is greater than a predetermined number, the rotation of the photoconductive drum is temporarily interrupted for every predetermined number of copies, so that the shape of a cleaning blade slightly changes, changing therefore the shape of the nip portion N, while the rotating photoconductive drum comes to a complete stop, and so that the change in the shape of the nip portion N causes the residual toner solidifying in the nip portion N to fall. This method can remove the residual toner only when the agglomerated residual toner is smaller in size; it cannot be said to be perfect.
Obviously, a machine with a high processing speed is required to have a long service life Therefore, it requires a method capable of satisfactorily removing the above described agglomerated toner on the photoconductive drum, for a long period of time, in order to maintain image quality at or above a predetermined level. Further, it is believed that in order to prevent the increase in the operational load and cost incurred when replacing a vibration generating means to maintain image quality at a predetermined level or higher, it is very important for the length of the service life of a vibration generating means to balance that of a cleaning apparatus or an image forming apparatus.
The present invention was made in consideration of the above described circumstances, and a primary object of the present invention is to provide a cleaning apparatus capable of satisfactorily removing the residual toner having agglomerated in the adjacencies of the cleaning blade, and an image forming apparatus equipped with such a cleaning apparatus.
These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings.